Login via JS

In UI tests, there's often a need to authenticate users. Instead of the slow and unstable process of entering login/password through the web interface, you can use API to get a token and set it in the browser via JavaScript. This significantly speeds up and stabilizes tests.

Why login via API in UI tests

Faster - we don't waste time entering login/password in each test. If you have hundreds of tests, this can take dozens of minutes.
More stable - no risk of failing due to captcha, redirects, or slow loading. If your goal is to test "how functionality works after login", not the login process itself, then such UI login only gets in the way.
Focus on functionality - we test business scenarios, not the login process itself. If your test, for example, checks "order creation in UI", it doesn't matter how the login form works - it should start already as an authenticated user.
Unification - you can use the same token in UI and API tests.
Bypass limitations - Sometimes the login form is protected (e.g., captcha or SSO through external service). Tests in CI won't pass such scenarios. In such cases, token or cookie via API is almost the only way to "login automatically".

Implementation and usage example

1. Authentication method in BaseUiTest

In BaseUiTest you need to create a static method that opens the browser, gets a token via API (which is significantly faster than through UI) and adds it to the browser's localStorage:

public static void authAsUser(String username, String password) {
    Selenide.open("/");
    String userAuthToken = RequestSpecs.getUserAuthHeader(username, password);
    executeJavaScript("localStorage.setItem('authToken', arguments[0]);", userAuthToken);
}

2. Token retrieval method in RequestSpecs

The getUserAuthHeader method from RequestSpecs class performs API login and returns a token (if the token is already in storage, it doesn't even make a request):

public static String getUserAuthHeader(String username, String password) {
    String userAuthToken;

    if (!authHeaders.containsKey(username)) {
        userAuthToken = new CrudRequester(RequestSpecs.unauthSpec(),
                ResponseSpecs.responseReturns200Spec(),
                Endpoint.AUTH_LOGIN)
                .post(LoginUserRequestModel.builder().username(username).password(password).build())
                .extract()
                .header("Authorization");

        authHeaders.put(username, userAuthToken);
    } else {
        userAuthToken = authHeaders.get(username);
    }

    return userAuthToken;
}

3. Usage in tests

Accordingly, in the test itself we first create a user and login using it:

@Test
void userCanCreateAccount() {
    CreateUserRequestModel user = AdminSteps.createUser();  // create user
    authAsUser(user.getUsername(), user.getPassword());    // login
    // then test steps follow
}